CVE-2024-50048
fbcon: Fix a NULL pointer dereference issue in fbcon_putcs
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fbcon: Fix a NULL pointer dereference issue in fbcon_putcs
In the Linux kernel, the following vulnerability has been resolved: fbcon: Fix a NULL pointer dereference issue in fbcon_putcs syzbot has found a NULL pointer dereference bug in fbcon. Here is the simplified C reproducer: struct param { uint8_t type; struct tiocl_selection ts; }; int main() { struct fb_con2fbmap con2fb; struct param param; int fd = open("/dev/fb1", 0, 0); con2fb.console = 0x19; con2fb.framebuffer = 0; ioctl(fd, FBIOPUT_CON2FBMAP, &con2fb); param.type = 2; param.ts.xs = 0; param.ts.ys = 0; param.ts.xe = 0; param.ts.ye = 0; param.ts.sel_mode = 0; int fd1 = open("/dev/tty1", O_RDWR, 0); ioctl(fd1, TIOCLINUX, ¶m); con2fb.console = 1; con2fb.framebuffer = 0; ioctl(fd, FBIOPUT_CON2FBMAP, &con2fb); return 0; } After calling ioctl(fd1, TIOCLINUX, ¶m), the subsequent ioctl(fd, FBIOPUT_CON2FBMAP, &con2fb) causes the kernel to follow a different execution path: set_con2fb_map -> con2fb_init_display -> fbcon_set_disp -> redraw_screen -> hide_cursor -> clear_selection -> highlight -> invert_screen -> do_update_region -> fbcon_putcs -> ops->putcs Since ops->putcs is a NULL pointer, this leads to a kernel panic. To prevent this, we need to call set_blitting_type() within set_con2fb_map() to properly initialize ops->putcs.
Reserved 2024-10-21 | Published 2024-10-21 | Updated 2024-12-19 | Assigner Linuxgit.kernel.org/...c/8266ae6eafdcd5a3136592445ff4038bbc7ee80e
git.kernel.org/...c/f7fb5dda555344529ce584ff7a28b109528d2f1b
git.kernel.org/...c/e5c2dba62996a3a6eeb34bd248b90fc69c5a6a1b
git.kernel.org/...c/5b97eebcce1b4f3f07a71f635d6aa3af96c236e7
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