860b3d066
Denys Vlasenko
2024-10-07
Subject
ash: command -v CMD must skip (go to next path) when CMD exists, but is not executable
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Commit Diff GitHub →
shell/ash.c+51 -3
| @@ -491,6 +491,11 @@ struct globals_misc { | |
| char **trap_ptr; /* used only by "trap hack" */ | |
| /* Rarely referenced stuff */ | |
| + | |
| + | /* Cached supplementary group array (for testing executable'ity of files) */ |
| + | int ngroups; |
| + | gid_t *group_array; |
| + | |
| #if ENABLE_ASH_RANDOM_SUPPORT | |
| random_t random_gen; | |
| #endif | |
| @@ -523,6 +528,8 @@ extern struct globals_misc *BB_GLOBAL_CONST ash_ptr_to_globals_misc; | |
| #define may_have_traps (G_misc.may_have_traps ) | |
| #define trap (G_misc.trap ) | |
| #define trap_ptr (G_misc.trap_ptr ) | |
| + | #define ngroups (G_misc.ngroups ) |
| + | #define group_array (G_misc.group_array) |
| #define random_gen (G_misc.random_gen ) | |
| #define backgndpid (G_misc.backgndpid ) | |
| #define INIT_G_misc() do { \ | |
| @@ -10171,6 +10178,7 @@ static int FAST_FUNC printfcmd(int argc, char **argv) { return printf_main(argc, | |
| #endif | |
| #if ENABLE_ASH_TEST || BASH_TEST2 | |
| static int FAST_FUNC testcmd(int argc, char **argv) { return test_main(argc, argv); } | |
| + | // TODO: pass &ngroups and &group_array addresses to test_main to use cached supplementary groups |
| #endif | |
| #if ENABLE_ASH_SLEEP | |
| static int FAST_FUNC sleepcmd(int argc, char **argv) { return sleep_main(argc, argv); } | |
| @@ -13782,6 +13790,43 @@ readcmdfile(char *name) | |
| /* ============ find_command inplementation */ | |
| + | static int test_exec(/*const char *fullname,*/ struct stat *statb) |
| + | { |
| + | /* |
| + | * TODO: use faccessat(AT_FDCWD, fullname, X_OK, AT_EACCESS) |
| + | * instead: executability may depend on ACLs, capabilities |
| + | * and who knows what else, not just mode bits. |
| + | * (faccessat2 syscall was added to Linux in May 14 2020) |
| + | */ |
| + | mode_t stmode; |
| + | uid_t euid; |
| + | enum { ANY_IX = S_IXUSR | S_IXGRP | S_IXOTH }; |
| + | |
| + | /* Do we already know with no extra syscalls? */ |
| + | if (!S_ISREG(statb->st_mode)) |
| + | return 0; /* not a regular file */ |
| + | if ((statb->st_mode & ANY_IX) == 0) |
| + | return 0; /* no one can execute */ |
| + | if ((statb->st_mode & ANY_IX) == ANY_IX) |
| + | return 1; /* anyone can execute */ |
| + | |
| + | /* Executability depends on our euid/egid/supplementary groups */ |
| + | stmode = S_IXOTH; |
| + | euid = geteuid(); |
| + | //TODO: cache euid? |
| + | if (euid == 0) |
| + | /* for root user, any X bit is good enough */ |
| + | stmode = ANY_IX; |
| + | else if (statb->st_uid == euid) |
| + | stmode = S_IXUSR; |
| + | else if (statb->st_gid == getegid()) |
| + | stmode = S_IXGRP; |
| + | else if (is_in_supplementary_groups(&ngroups, &group_array, statb->st_gid)) |
| + | stmode = S_IXGRP; |
| + | |
| + | return statb->st_mode & stmode; |
| + | } |
| + | |
| /* | |
| * Resolve a command name. If you change this routine, you may have to | |
| * change the shellexec routine as well. | |
| @@ -13808,9 +13853,12 @@ find_command(char *name, struct cmdentry *entry, int act, const char *path) | |
| if (errno == EINTR) | |
| continue; | |
| #endif | |
| + | absfail: |
| entry->cmdtype = CMDUNKNOWN; | |
| return; | |
| } | |
| + | if (!test_exec(/*name,*/ &statb)) |
| + | goto absfail; |
| } | |
| entry->cmdtype = CMDNORMAL; | |
| return; | |
| @@ -13923,9 +13971,6 @@ find_command(char *name, struct cmdentry *entry, int act, const char *path) | |
| e = errno; | |
| goto loop; | |
| } | |
| - | e = EACCES; /* if we fail, this will be the error */ |
| - | if (!S_ISREG(statb.st_mode)) |
| - | continue; |
| if (lpathopt) { /* this is a %func directory */ | |
| stalloc(len); | |
| /* NB: stalloc will return space pointed by fullname | |
| @@ -13938,6 +13983,9 @@ find_command(char *name, struct cmdentry *entry, int act, const char *path) | |
| stunalloc(fullname); | |
| goto success; | |
| } | |
| + | e = EACCES; /* if we fail, this will be the error */ |
| + | if (!test_exec(/*fullname,*/ &statb)) |
| + | continue; |
| TRACE(("searchexec \"%s\" returns \"%s\"\n", name, fullname)); | |
| if (!updatetbl) { | |
| entry->cmdtype = CMDNORMAL; | |